11) ventilation and endurance performance do … lung physiology.pdf · 11) ventilation and...

Cycling Articles: Physiology 11. Lung Physiology1

11) VENTILATION AND ENDURANCE PERFORMANCE Do our lungs limit how fast we can go?

So far, on the MAPP I have devoted a lot of attention to two major organsystems that are intimately linked in exercise performance, the skeletalmuscles and the cardiovascular system. Now I want to factor a third, equallyimportant system into the equation, the pulmonary system. I am going todiscuss breathing and exercise.

The term ventilation is used in physiology circles exclusively in reference togas exchange in the lungs. You will also see the word respiration, butexercise physiology types often like to reserve this word for use in a cellularmetabolism context, so I will try to use ventilation when I mean breathing.Now, when you hear a non-smoker trapped in a smoke-filled room gaspingsomething about "this room needs better ventilation," she means that theroom does not have very rapid air-exchange with the outside, smoke-free air.Conversely, in a room that is well-ventilated, the air always seems fresh evenwhen lots of people are crammed together in a small enclosed space, suckingin oxygen and blowing out lots of "waste-products." You non-physiologistsprefer to call this situation "a party."

Rooms depend on air-conditioning systems, or big windows and a breeze forventilation. Our body depends on the lungs, the diaphragm and severalintercostal muscles, and a sensitive feedforward/feedback controlledregulatory system to control them. The purpose of the lungs is to ventilate theblood. Blood is the transport vehicle that carries oxygen to all of our cells, andcarts off the constant production of CO2 that is produced as a by-product ofboth metabolism and pH buffering. The lungs are the site of pickup from anddelivery to, the atmosphere. The greater the demand for oxygen delivery andCO2 removal, the greater the air volume that must circulate in and out of thelungs each minute. All animals of any size at all have had to come up with aventilation system to get oxygen from the atmosphere down to the mosthidden of the cells via the blood. Fish have gills. Insects have a system of airtubes called trachea. We mammals own beautiful pink lungs.

Three aspects of ventilatory function: air exchange, O2/CO2 exchange,and blood-gas carrying capacity

1. Air Exchange: Moving air in and out of the lungs


Sitting here in front of my computer, I am breathing about 12 times per minute(although if I try to count my own breathing rate, it will change because I amthinking about it). So my ventilatory frequency (Vf) is 12 breaths/min. Eachbreath has a volume of about 0.75 liter. This is my resting tidal volume, thevolume of air flowing in and out of my lungs each breath. Multiplyingventilatory frequency (Vf) times tidal volume (TV) gives me ventilatory volume(VE), which is 9 liters/min in my example. This is the volume of air moving inand out of my lungs each minute. Somewhere in my files, I have the datafrom one of the VO2 max tests I did as a graduate student. During that test,my ventilatory volume (liters/min) peaked at 187 liters/min. That is over 20xgreater than at rest. How do our lungs meet the demands of exercise?

Ventilation is regulated in much the same manner as cardiac output. Theheart increases cardiac output by increasing both stroke volume and beatingfrequency. The respiratory nerves control ventilation similarly. At low exerciseworkloads, the dominant ventilatory adjustment is an increase in tidal volume,the volume of air being moved in and out of the lungs each breath. At highworkloads, an increase in breathing frequency is the primary adjustment. Thetwo figures below visualize this. The first figure shows the overall ventilatoryresponse during a treadmill test with progressive increases in velocity every60 seconds, and a constant incline of 5%. The second figure breaks theventilatory response above into breathing frequency and tidal volume. This isreal, unsmoothed data collected during a test of a well trained runner.


Unlike heart function, ventilation is under considerable voluntary control (withinvoluntary override mechanisms!). So, you might ask the question, "Can Icontrol my breathing to make it more efficient?" For example, you coulddecrease the breathing frequency and take bigger deeper breaths to achievethe same total ventilation volume. Studies have indicated that normally thebody spontaneously balances the depth of ventilation and the frequency ofbreathing so that ventilation is optimally efficient. You may also have noticedthat at low exercise intensities, you can "play" more with your breathing, byvarying its rate and depth. However, as the workload gets high, especially atworkloads above the lactate (and ventilatory) threshold, the body assumesmuch tighter control on breathing and there is far less room for variation inbreathing "strategies."

The actual act of moving air in an out of the lungs is accomplished in muchthe same way that a bathroom plunger works. Since the thorax is "sealed,"


expanding its volume causes air to rush into the lungs to fill the relativevacuum. When we inspire air, we do so by contracting the diaphragm, pullingit down (similar to pulling up on the plunger). If you are breathing "correctly" atrest, the main movement you will notice is your stomach bulging out a bitduring inspiration. This is because the diaphragm is pressing down againstthe abdominal cavity. You are "belly breathing." At rest and low ventilationvolumes, this is enough. However, when we need to move a lot of air in andout of the lungs, we not only increase the force of diaphragmatic contraction,we also contract muscles attached to the rib cage. This pulls the ribs up andout, further expanding the thorax and allowing more air to rush into to thelungs. All of this takes muscular work, so inspiration is an "active process."Expiration, or blowing the air back out, is basically a matter of relaxation whenwe are at rest. The elasticity of the muscles and tissues is sufficient to pushthe air out. The process becomes more demanding as we exercise harder.During heavy exercise we exhale more forcefully and deeply in order toensure more rapid and complete exhalation of the old air. This process alsotakes energy in the form of muscular work. So, the bottom line is thatbreathing is not free to the body. And, it gets more energetically expensive athigh workloads. I will come back to this point later.

2. Gas exchange: Moving oxygen and carbon dioxide on and off the redblood cells.

OK, now that we are moving the air in and out of our body, let's turn ourattention to the lungs, and "get cellular" in our thinking. The lungs do somepretty cool stuff. The lung's challenge is to mix air and blood thoroughly andrapidly so that gas exchange can occur. Here comes another analogy. Let'ssay you have a gallon bucket (4 liters) of paint sitting with the lid open. Howlong will it take that bucket of paint to dry out? Days and days. But, if wespread the paint as a very thin layer over a very large wall, it will be dry in notime. By spreading the paint out we increase the total area of exposedsurface between the paint and the air thousands of times and the water in thepaint is quickly evaporated. At any given instant at rest, the lungs spreadabout 70 ml of blood (less than half of the volume of a coke can) in a "sheet"of capillaries with a total surface area of 70 square meters. That is likespreading a gallon of paint thin enough to paint a football field! The capillariesare so narrow that the red blood cells actually have to squeeze through. Thisalso insures that the gas exchange across the red blood cell and capillarymembranes is lightning fast. Simultaneously the lungs move the inspired airdown a system of 23 branches of air passages terminating with about 300million tiny spherical alveoli that form the terminal exchange tissue in the


bronchial system. These two exchange systems, the alveoli for air, and thecapillaries for blood, are intertwined so microscopically close that oxygen andcarbon dioxide molecules diffuse across the membranes and equilibratealmost instantaneously. Blood passes through the capillaries in about 0.8seconds at rest and as little as 0.4 to 0.5 seconds during hard exercise. It isduring this very brief exposure period that all the gas exchange between eachred blood cell and the air in the lungs must take place before each return tripto the body!

Now perhaps one of you physiology student types is doing some analyticalthinking that does like this: If resting cardiac output is 5 liters per minute, andmaximal cardiac output were say, 25 liters/min, that would mean that 5 timesas much blood passes through the lungs (and back to the heart and then tothe body) and those capillaries per minute at max. Why doesn't the lungcapillary transit time for each blood cell decrease from 0.8 secs at rest to0.8/5 or a really fast 0.16 seconds during maximal exercise? Here is theanswer. Normally, the lungs only use a fraction of the total capillary volumeavailable. Small arterioles can regulate the entry of blood into portions of thelungs. During exercise this restriction is gradually removed and the capillaryvolume can increase by over 3 fold to about 250 ml. This helps to minimizethe decrease in capillary transit time. It does not eliminate it though. Howimportant is that? This is another point which we will hit on again.


3. Blood-gas transport: Delivering oxygen to the muscles

Now let's think about how the blood fits into all of this. Blood serves severalimportant functions during exercise (heat removal, deacidification, glucosedelivery, hormone communication to name a few), but the one I want to focuson is its role as a delivery truck for oxygen. About 40 to 50% of the totalvolume of blood is made up of red blood cells (RBCs). For example, if your"hematocrit" is 43, then 43% of your total blood volume is RBCs. More thananything else, RBCs are just tiny, flexible sacks of hemoglobin. Each RBCcontains hundreds of hemoglobin molecules, and each hemoglobin moleculehas room to carry exactly 4 oxygen molecules. When I say "carry" I mean"bind" in chemistry lingo. There is some very fancy chemistry going on herethat we would be in deep trouble without, but I will not try to explain it otherthan to say that hemoglobin molecules are engineered to hold on to oxygentightly enough to carry it out of the lungs, but loosely enough to release it inthe capillaries feeding the skeletal muscles (and other organs of course). Thiswhole process is designed to function best when the atmospheric pressure isnear sea level. If we get 1500 meters or more higher than that, the systembegins to break down, and hemoglobin leaves the lungs without a full load ofoxygen. This is why it is more difficult to breathe and exercise at altitude.

The capacity for blood to deliver oxygen can be summed up using anequation:

Hemoglobin concentration X oxygen binding capacity of hemoglobin(ml O2/g hb) X percent saturation of hemoglobin = oxygen carried in agiven volume of blood.

Hemoglobin concentration is expressed in grams of hemoglobin per deciliterof blood (g/dl). Typical values range between 12-14 for women and 14-16 formen. The binding capacity of hemoglobin for oxygen is a constant and equals1.34 ml O2/g hemoglobin. Finally, the percent oxygen saturation ofhemoglobin when it leaves the lungs is normally about 96% (it is not 100%largely because the lung tissue has its own blood supply and this smallvolume of deoxygenated blood mixes in with the fresh stuff).

So, for an average person with a hemoglobin of 15, the oxygen volumecontained in each liter of delivered blood will be:

15g/dl x 1.34 ml O2/g hgb x 0.96 saturation x (10dl/l) = 193 ml O2/ literblood.


If we substitute in 12 for the hemoglobin concentration (someone withanaemia) and 18 (a very high value occasionally seen in trained athletes athigh altitude), we see that for the same cardiac output, the volume of oxygencarried by the blood would vary between 154 and 232 ml per liter, dependingon the hemoglobin value. It is not hard to see how the blood oxygen carryingcapacity affects the VO2 max. Remember, the muscles can only use what theheart can deliver.

If hemoglobin concentration is higher, the blood can carry more oxygen. Thisis an important point with relevance to altitude training, illegal EPO use,gender differences in VO2 max, anaemia etc. (I should note here that there isa downside to increasing haemoglobin concentration in the blood and that isincreased blood viscosity. The body normally maintains an appropriatebalance. If the blood becomes too thick, flow resistance increases and therisk of blood embolism increases, hence the dangers of EPO use.) Second,when the blood leaves the lungs it is normally fully saturated with oxygen.This means that the lungs are very effective at ventilating the blood, even inuntrained folks. This is one of the reasons why in the big scheme of things webasically disregard lung function as an area for improvement in the athlete'sendurance machine. But, this issue is worth taking a closer look at.

Ventilation Issues in Endurance Performance

Is ventilation volume a limiting factor to maximal endurance?

Sometimes you hear people say "I ran out of wind." Is that really possible?Can we reach a point in exercise when ventilation just can't keep up withdemand? The answer is no, assuming you don't have acute asthma or someother severe pulmonary dysfunction. We can measure a person's maximalvoluntary ventilation (MVV), the maximal volume of air they can breath in andout while at rest, and compare it with their maximal ventilation duringexercise. What we see is that untrained people only use about 60 to 85% oftheir maximum ventilatory capacity even at maximal exercise. For examplethe MVV for an average male might be nearly 200 l/min. However, during atreadmill VO2 max test, they reach a peak ventilation of only 140 l/min. Highlytrained athletes use more of their capacity, perhaps over 90%, but ventilationcapacity is still not a limitation on performance. Unlike the story with cardiacoutput, even during maximal exercise, the ventilatory capacity is not maxedout.


By the way, the highest ventilation volume I have read about in a human was263 l/ min recorded on a really big male rower with a chest about the size of abeer keg. Ventilation volumes in excess of 200 l/min have also been recordedin elite female oarswomen. Understandably, rowers get most of the bigventilation prizes because they are really big for endurance athletes, at leastamong humans. The highest ventilation rates I have heard about in anyathlete, irrespective of species, was in a racehorse. They have ventilationvolumes of about 1500 liters/min!

Does ventilation performance decline as we get older?

Data from Åstrand presented in his Textbook of Work Physiology addressesthis question. He compared ventilatory parameters in a group of male andfemale physical education students when they were in their 20s, again whenthey had reached their 40s, and a third time when they were in their 50s. Thelongitudinal study covered 33 years in all. While other aspects of the students’capacity declined, basic lung function was very stable. Total Lung Capacitywas unchanged. Maximal Tidal Volume was unchanged and MaximalVentilation during exercise was only decreased a few percent in 33 years.One change that does seem to occur consistently due to aging is an increasein the "residual volume" as a percentage of total lung capacity. This meansthat less of the actual lung volume is dynamically used during ventilation. Thisage-related change can be accounted for by loss of lung elasticity with age.Overall though declining lung capacity does not seem to be a big factor in theperformance limitations of the aging athlete. Lung function is not the weak linkin endurance performance, assuming you stay away from the cigarettes.

Uncomfortable Positions- Can body position influence ventilationcapacity?

Now, one issue that needs to be considered when we discuss ventilation isbody position. In most sports situations the chest is very free to expand.Running and cycling do not impose any mechanical limitations on ventilation.Even down in the aerodynamic position, maximal ventilation in cyclists doesnot appear to be compromised. However, swimming adds resistance tobreathing because we have to move both the ribs and the water surroundingthe body when expanding the chest. Coupling this with the problem ofcoordinating breathing with the brief periods of time the mouth is out of thewater probably results in a relative under-ventilation in swimming.


Ventilation during rowing: Special Problems?

Another sport that has gotten some special attention from the ventilation folksis rowing. This I know more about, so I will elaborate a bit. During rowing, thebody is squeezed up with the chest against the knees over 30 times a minute,limiting diaphragmatic excursion. That might create some breathing problems,but it is not the biggest issue. The real issue is the fact that rowers also usethe same abdominal and intercostal muscles used for breathing to supportthe back during the powerful extension employed each stroke. Rowersisometrically contract all of these muscles to apply a high interthoracicpressure at the moment of the catch, when the oars take the water, toreinforce the connection between oar, back and legs. It is impossible tobreathe and constrict all the abdominal and thoracic muscles at the sametime.

The consequences of this competition are debated. The results of several,but not all studies suggest that elite rowers are not able to achieve the sameventilation volume at max during rowing as they achieve during cycling. Thedifferences are not huge, but they may be significant. For example in onerecent study elite rowers achieved a peak ventilation of 198 l/min during aVO2 max test cycling, but only 171 liters/min during rowing. The VO2 maxvalues for the rowers were not different between rowing and cycling (5.03l/min vs 5.09 l/min). This suggests that the small degree of under-ventilationat max experienced in rowing does not limit maximal oxygen consumption.However, some physiologists interpret these results differently. It is generallyaccepted that elite endurance athletes achieve their highest values of VO2max when they are performing the sport that they train for. In other words,elite runners excel most during treadmill tests. Elite cyclists max out slightlyhigher on cycling tests etc. In several studies national class rowers havedemonstrated the same VO2 max while rowing as they did while running, oreven cycling. This has not been a unanimous finding, but it appears that VO2max for highly trained oarsman during rowing is lower than it "should be",when consideration is given to their training specificity and the very largemuscle mass employed in rowing. A mechanism for this problem may be aslight ventilatory limitation imposed by the unique demands of rowing.Personally, I am inclined to believe that VO2 max is limited in rowing for adifferent reason. The muscle contraction frequency is two slow and at toohigh intensity to allow optimal blood flow to the working muscles, and musclepump action by the working muscles. If this is true, then higher stroke ratesmight produce increased aerobic power. This is consistent with the trend inelite rowing to move toward higher stroke rates, but it is not proven. But, now


that I have mentioned stroke rates, that brings up another interestingventilation issue.

Breathing to the beat: Entrainment of ventilation rate to movementrhythm

If my wife joins me at the rowing club for a workout on the rowing machines,an interesting phenomenon occurs. Hilde is not a rower, so she alwaysseems to adjust her rowing cadence so that it matches mine. I don't think shedoes it on purpose, but her rowing rhythm naturally entrains onto mine. Thisis problematic when I am doing intervals and she is rowing steady state! Ourventilatory system does the same thing. Ventilation tends to match withrunning, cycling or rowing cadence in a consistent pattern. For example, incycling, we sometimes see athletes exhale in unison with the downward kickof the same leg, every 2nd or third stroke. This entrainment process does notseem to be a bad thing. In fact, since it is more prevalent in experiencedathletes, it is probably an adaptation that promotes efficiency by minimizingthe mechanical constraints to breathing created by limb movements.

Breathing pattern seems to be an especially important issue in rowing.Steinacker et al (1992) investigated ventilatory responses during incrementalrowing exercise and observed two distinct breathing patterns. Type 1 wasone complete breathing cycle per stroke cycle, with expiration occurringduring the drive and inspiration during the recovery phase. Type 2 was twocomplete breaths per stroke, one during the drive and one during therecovery. When the intensity reached a certain point, the rowers automaticallyswitched from type 1 to type 2. All these elite male rowers entrained theirbreathing to the stroke rate. Another study found the same patterns in elitefemale rowers. Untrained subjects tested during rowing only rarely exhibitedthis pattern. To make things more interesting, it appears that the breathduring the stroke is "smaller" than the breath during the recovery phase.

Now if we extrapolate those findings to a racing situation at a high 40 strokesper minute, what we would expect is a ventilation rate of 80 breaths perminute. This is very high! In running or cycling max tests we usually seemaximum ventilation rates of about 50 to 60. In contrast, ventilation rates ashigh as 88 breaths per minute have been observed during competitiverowing, accompanied by a relatively low tidal volume. All of this data suggeststhat the mechanics of rowing place unique demands on ventilation. Welltrained rowers adapt to these demands by developing very strong ventilatory


muscles and adapting a unique breathing rhythm which makes the most ofthe brief periods of relaxation during the stroke.

The Great Arterial Desaturation Debate

New topic. Earlier in this breath-taking novel of mine, I discussed the issue ofhemoglobin saturation with oxygen. I said that the lungs were so good atoxygenation that the blood always leaves the lungs saturated with oxygen,even during hard exercise when cardiac output is high. This means everyRBC picks up a full load of oxygen before leaving the lungs. Now I am goingto contradict myself a bit.

Here is the central issue. The blood returning from the periphery musteliminate its carbon dioxide load and fully re-saturate with oxygen during thebrief time it passes through the lung capillary network on the way backthrough the heart and out to the body again. Normally this is not a problem. Itonly takes about 0.45 seconds for the hemoglobin to become fully saturatedduring its passage through the twisting capillaries. It takes even less time tounload the CO2. Since the transit time is 0.8 seconds, there is time to spare.Even during exercise there is enough time, unless......you are a really fitathlete with a very high cardiac output and VO2 max.

Recent studies with highly trained endurance athletes (VO2 max over 70ml/kg/min) have shown a significant degree of arterial desaturation. Thismeans that for the guys with the really big cardiac outputs, the blood isrushing through the lungs so fast that hemoglobin hasn't taken on a full loadof oxygen before leaving for the muscles. The result is that instead of being96 or 97% saturated with oxygen, the blood leaving the lungs may only be 89or 90% saturated in the athletes with very high cardiac outputs and VO2 max.Clifford et al. (1990) reported a drop in arterial saturation from 105 mm Hg atrest to 88 mmHg during the last minute of a maximal rowing test in eliterowers. This means that the arterial blood was becoming slightly hypoxicwhen they reached very high workloads. All other things being equal, VO2max might be up to 5 % higher or so in the elite types if the lungs could fullysaturate the blood at maximal cardiac output. Support for this assumptioncomes from the fact that when well trained athletes breathe a higherconcentration of oxygen while performing in a lab, they reach a slightly higherVO2 max.

What does this information mean in regards to how we train? Nothing. Thereis nothing we can do to prevent this desaturation in folks with the really high


cardiac outputs, short of having them wear an oxygen tank while performing.Unless you have a VO2 max of about 5 liters/ min or higher, it is not really anissue anyway. Consider arterial desaturation a small physiological tax on the"cardiovascularly endowed."

The Rising Cost of Breathing

The ventilatory muscles, like all muscles need oxygen to support continuousexercise. It turns out that the diaphragm is one of the body’s best endurancemuscles, perhaps even in second place behind the heart. It has a highpercentage of type I fibers, a high capillary density, and high concentration ofoxidative enzymes, compared to skeletal muscles. Animal studies havedemonstrated that the diaphragm improves its endurance capacity(mitochondrial enzyme concentration) with training, but not more than about20-30%, because it is already pretty well equipped for chronic work. However,with high intensity training, other muscles involved in breathing like theinternal and external intercostals and the abdominal muscles become moreactive and also improve their endurance capacity. Since these muscles areless trained to begin with, they respond more to endurance training. Theseaccessory breathing muscles are not trained at low exercise intensities butbecome active when we really start moving a lot of air.

From the above, plus your own experience, you can figure out that breathingbecomes more demanding when ventilation rates get very high. There arestudies which have actually measured the oxygen cost of breathing atdifferent intensities. You might think of this as the tax on oxygen delivery. Thebody has to deliver blood to the ventilatory muscles so that they can help thelungs supply oxygenated blood to the rest of the body. To make things worse,this “tax rate” increases when you are working at very high intensities. Theoxygen cost per liter of ventilation (VE) doubles from low to very high exerciseintensities.

The bottom line is that while the oxygen cost of breathing is only perhaps 3-6% of total VO2 at low intensities, it can be as high as 10 to even 15% of totalVO2 in young adults with greater than average VO2 max. In the fit olderathlete, a high oxygen cost of breathing may occur at lower ventilation ratesdue to the increased stiffness of the chest wall.

Because physical training results in a reduced ventilatory response (at anygiven level of CO2 production) during intense exercise, in the highly trained,the high cost of breathing is somewhat reduced. One interesting physiological


question is whether or not the respiratory muscles “steal” blood flow from theskeletal muscles at intensities near VO2 max. The scenario goes like this.Cardiac output has already maxed out, but hyperventilation is still climbing, sothe respiratory muscles need more oxygen. Physiologists have predicted thatthe respiratory muscles would get their share of blood flow at the expense ofskeletal muscle blood flow, but direct experiments are lacking. Does thismean VO2 max would decrease? No, it would be the same. However, thepeak work rate achieved at VO2 max would be reduced, because more of theconsumed oxygen is going to supply “supporting organs” instead of theskeletal muscles.

When you add this to the problem of desaturation, we see that there aresome additional limitations on maximal performance that enter into the picturewhen we start dealing with extremely well trained endurance athletes. Theseguys have such high cardiac outputs and work capacities that the ventilationmachinery starts to demand a lot of the total available oxygen in order to keepthe machine running.

Do the Breathing Muscles Fatigue?

The final issue I want to discuss brings us back to a common theme inendurance performance, muscular fatigue. We know the skeletal musclesfatigue (lose force generating potential) during endurance exercise. Do thebreathing muscles get tired?

To make things short and sweet it appears that they do fatigue. Tests ofmaximal ventilatory function after a hard endurance session show atemporary drop in, for example peak expiratory force. This is an indirect wayof measuring how much force the diaphragm can generate.

But, does fatigue of the ventilatory muscles limit performance?

To date the best technique for answering this question is to unload theventilatory muscles and observe whether performance improves. Thesetechniques have included using helium oxygen mixtures and breathing assistdevices. Unfortunately, the methodology is not perfect. For example, usinglighter than air helium may make the hoses and mouthpiece easier to hold inthe mouth and actually decrease the cost of rowing. The results are unclear.At workloads below 85% of VO2 max it appears the respiratory fatigue has noinfluence on performance. However, the results of some studies suggest thatat intensities approaching VO2 max respiratory fatigue may contribute to


performance limitations. The scientific jury has not reached a verdict on thisquestion.

Can I Apply Any of This to My Training?

So, if you made it to the end of this novel, you may be disappointed to learnthat there are no secret breathing tricks that will push you over the top. Ingeneral the lungs are wonderfully equipped for doing their job. Training doesimprove the ventilatory system in some ways, but it is not the weak link inhealthy athletes. In recent years, there have been a handful of studiespublished where the impact of inspiratory muscle training on various aspectsof pulmonary and endurance performance have been investigated. Thisinvolves essentially weight training for the breathing muscles, whereresistance is generated by using some kind of device that reduces airflowduring inspiration and forces the inspiratory muscles to work harder againstgreater resistance. Neither peak pulmonary function nor maximal oxygenconsumption have been shown to change with this form of training. However,a couple of studies have shown modest increases in either time to exhaustionor time trial performance during cycling, using placebo controlled designs.How does this work? Perhaps stronger inspiratory muscles allow highventilation to be achieved at lower breathing frequencies. This woulddecrease the oxygen cost of breathing and free up some blood flow for theworking muscles. Perhaps.

If there is another area where we can benefit from attention to breathing, itwould be the issue of entrainment. Good athletes develop breathing“rhythms” that tune in to the rhythms of their movements. This probablypromotes efficiency. When you feel yourself performing at your physiologicalredline, your breathing may be a place to turn your attention. If you are arunner or cyclist, focus on the diaphragm and the abdominal muscles formoving the air in and out, instead of the intercostals attached to the chest.Heaving the chest more than necessary costs extra energy. “Belly breathing”makes sense. If you are a rower “belly breathing” doesn’t work too well. Wejust have to learn how to breathe between the strokes.

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